The present invention relates to a directional coupler used as an optical component and an optical communication device using the same.
A conventional directional coupler has a structure in which a directional coupler is two-dimensionally formed with respect to a substrate. Therefore, if a plurality of directional couplers is integrated, an area occupied by the directional couplers in a device is increased.
In order to solve this problem, technology for realizing a three-dimensional structure has been proposed as disclosed in Japanese Patent Application Laid-open No. 5-224049, for example.